Spark plug



DBC. 24, 1940. F, KAPP 2,226,414

SPARK PLUG Filed Sept. 16, 1939 v INVENTOR.

FRED K PP ATTO Patented Dec. 24, 1940 UNITED sTATEs PATENT OFFICE 3Claims.

This invention relates to improvements in spark plugs for internalcombustion engines of the type having a central electrode which extendsthrough a passage provided in a porcelain or equivalent ceramic materialinsulator, which insulator is secured in place within a metallic outershell or casing having a second electrode arranged in sparking relationto the inner end of said central electrode, and the principal object ofthe invention is toprovide certain improvements in and relating to thecentral electrode structure and its relation to the insulating member,whereby there is provided a spark plug which, after severe use, willremain gas-tight and will fire at high working pressures in modern highcompression automobiles, trucks, tractors, and other types of motors atevery ignition cycle.

A further object of the invention is to produce the hottest possiblespark and, at the same time, .gsuring a perfect combustion in the iiringchamr. A further object of theinvention is to provide an insulatedcentral electrode equipped with three compression seals, thus forming agastight spark plug insulator.

An additional object of the invention is to provide a spark plug havinga V-type ground and a central electrode, said V-type ground providingtwo top spark surfaces wherein the spark functions to heat ilrst, saidcentral electrode serving to split the supplied spark for two parelleichannels, thus keeping the spark alive longer and producing a hotterspark for better combustion.

of this speciilcation and in which like numeralsare employed todesignate like mrts throughout the Same,

iiexible cemented arresting ring and the short flattened one-half turntwisted. knurled and grooved portion of the central electrode;

Fig. 3 is a horizontal section through the ring, the view being taken onthe line 3-3 of Fig. 1;

ywhole the grounded or shell electrode.

. Fig. 4 is a similar sectional view taken on the line 4 4 of Fig. 1;andv Fig. 5 is a plan view of the asbestos ring that forms part 'of myinvention.

In the accompanying drawing wherein for the 5 purpose of illustration isshown a preferred embodiment of my invention, the numeral 1 designates ahollow metallic vshell or casing of a spark plug adapted to receivetherein an insulated core 8. the detailed construction of which lil willbe hereinafter described. The said casing has its lower portionexternally threaded as at 9 to engage an opening in the cylinder of aninternal combustion engine, while its upper portion is formed with anangular head I0, whichl can be engaged by a wrench for attaching theplug in place. The numeral il indicates a gland nut that has threadedconnection withinternal threads i2 oi the angular head I0 of the sparkplug casing. The said nut serves to retain in 20 place the insulatedcore 8 after it has been fitted in the hollow casing l.

Extending through the bore i3 of the insulated core is the primary orcentral electrode, designated as a whole by the reference character A,25 while the referencecharacter B designates as a As illustrated toladvantage in Fig. i, it will be noted that the upper end of'theelectrode is threaded as at it and receives thereon -a nut i5 utilizedin 3G fastening it to one oi the current wires of the ignition system.Integrally formed with the centrai electrode is a flange i8 and anenlarged head l1, the latter adapted to be received in the en- 'largedbore II of the core, while interposed be- 35 tween said flange and theupper end I8 of the insulated core is a pair of gaskets-one of aluminum,as indicated by the numeral I9, and the other of asbestos material, asindicated by the numeral 20. In my years of practical experience withspark plugs, I have-"found, by examining old and new plugs to ascertainthe reason for failure, that the main reason for loss of edectivenesshas been the `absence oi' a proper compression seal around 45the'central electrode, whereby the heat escaped outside o the centralelectrode through the top seal gasket and the upper insulated opening,thus causing'a loosening of the cement which is applied on the plaincentral electrode surface, which loosening action has been occasioned bythe escaping compression and heat.4 Accordingly, the

' .cement has'lost its binding strength when it has become too hot.

It is for this reason that I have eiiected the assembly of the aluminumgasket .I9 and the asbestos gasket 20; and by virtue of the constructionemployed, the asbestos gasket is pressed to the top of the insulatedopening by the alu- 5 mlnum gasket i9, and an effective compression sealis realized.

Spaced from the head il and secured to the central electrode A is asmall flexible ring 2l that is preferably fastened throughthe center lof the shaft of the electrode and wound around one complete turn. Thisring functions to hold the cement 22 while the latter is soft and whenassembled to the insulator body, the ring acts as a stop for the cement.Accordingly, when the l cement has become hard and dry, a gas-tightsafety seal is assured, which, to my knowledge, does not exist in anyother type of spark plug.

Formed on the shaft of the electrode is a knurled member 23 that is of asubstantially fiat one-half turn twisted form, provided with a knurledsurface as at 2l and barbs as at 25, which member 23: retains the cementabsolutely tight on its roughened surfaces and the inner insulator walland presents, when subjected to a 25 light twist, a vibration on itsupper end. It will be observed, at the same time, that even if .the topterminal is broken on', there is still assured a gas-tight compressionseal, and the spark plug will continue to fire as long as the damagedpart makes the contact with the remaining part of the central electrodein the spark plug insulator.

As disclosed to advantage in Fig. 1, the numeral 2B indicates thethreaded portion of the central electrode A that is threadedly securedto l the lower insulator shoulder of the spark plug insulator. Thenumeral 21 indicates a gland nut gasket interposed between the lower endof the gland nut and the annular upper outer shoulder 28 of the casing1, while the numeral 29 indicates the plug seat or shoulder on which ispositioned a sealing and cooling gasket 30.

I wish to herewith supplement the features of construction of the plug,as above described, with a statement of facts relative to the reason fordevising said construction.

'I'he plain electrode system does not carry enough binding cement toproduce the desired effect around its axis, and, therefore, whensubjected to higher temperature and severe service,

will loosen up, even on some new spark plugs. Most of the enginesmanufactured have increased compression pressures, but the fact remainsthat spark plug failures, mainly, current leakage under high workingpressures, have not been brought under satisfactory control. Theprovision made in this invention will eliminate central electrodeoverheating and current and compression leakage through the medium ofthe spark plug central electrode around the spark plug insulator,

e0 thus resulting in longer plug life.

It is a well-known fact that spark plugs that leak compression andcurrent become hotter. The said leakage throws the plug out of itsproper heat range, and the electrode under' these conditionsdeteriorates faster, swells up in diameter, and `causes insulator firingtip breakage that sometimes results in costly engine wear and loss ofpower.

Mechanical characteristics of a spark plug vary with the type of motorand service conditions in which they are used. While a spark pluginsulator may show satisfactory results under a cool test, nevertheless,it is liable to leak when hot under compression. Coolcompression testsare i not sufficient. The leakage for a new spark plug shall not exceeda iixed'maximum. The resistance path from the central electrode to themetal body of a spark plug shall not be less than a predeterminedminimum. My particular plug conforms in every respect to the Federalspecifica- 5 tion for spark plugs.

I wish to further point out that plain central electrodes in the liquidcement, when subjected to heat and severe conditions, do not give enoughbinding strength to maintain a safe compression l0 seal. I have,accordingly, proposed in the present invention to produce a gas-tightspark plug central electrode wherein asafe compression seal will bemaintained.

The most serious trouble in all spark plugs is 15 spark plug leakage;and, accordingly, the'rst gas-tight compression seal in a spark plugshould be provided as close as possible to the spark plug insulatorlower shell seat and shell inside the gasket for faster dissipation ofthe heat from the 20 central electrode and insulator firing tip. This Ihave accomplished by the provision of the sealing and cooling gasket 30.

Likewise, in the present invention the danger of the loosening 'of thecement binding that 25 causes plug overheating is reduced to a minimum,fast electrode deterioration is eliminated, and every effort has 'beenexpended to produce a plug, by the construction employed, that will notbe thrown out of balance, and loss of power and 30 poor motorperformance will not be experienced.

I have, accordingly, provided a new spark plug central electrode withthree gas-tight compression safety seal features, which plug iseconomical to manufacture, and wherein outside moisture is 35 preventedfrom reaching the operative parts of the spark plug. Further, the newflexible wire cement stopper positioned around the upper centralelectrode shaft serves to hold the cement While soft and when assembledto the insulator body safe in its proper intended second compressionsafety sealing place, and, accordingly, when dry and hard, a gas-tightsecond compression safety seal is assured, which, to my knowledge, isnot found in any other spark plug.

It is to be understood that the form of my invention herewith shown anddescribed is to be taken as a preferred example of the same and thatvarious changes relative to `the material, size, shape and arrangementof parts may be resorted to without departing from the spirit of theinvention orthe scope of the subjoined claims.

Having thus described my invention, I claim:

1. In a spark plug equipped with a metallic housing having a groundelectrode provided therein and an insulating member positioned withinsaid housing, of a central electrode having a portion thereof threadedlysecured within said insulating member, means carried by said electrodeadapted to cooperate with cement positioned within said insulator toeffect a compression seal, said means comprising a ring carried by saidcentral electrode, and a distorted member formed integral with saidlelectrode and having a barbed and lserrated surface, said central 65electrode being threaded throughout a portion of its length.

2. In a spark plug equipped with a metallic housing having a groundelectrode provided therein and an insulating member positioned in saidgo housing, of a central electrode having a portion thereof threadedlysecured within said insulating member, means carried by said electrodeadapted to cooperate with cement positioned within said insulatingmember to eil'ect a compression seal, f

sulating xnember, the cooperating threads providing a primarycompression seal, and means formed integral with said central electrodeincluding a distorted barbed portion capable of cooperating with cementpositioned within said insulator and adhering to said distorted barbedportion to effect a supplemental compression seal.

FRED KAPP.

